Here’s a dirty secret of the RC industry: a lot of the time, nobody is actually quality-checking the antennas they sell you. The antennas are usually designed correctly. Then they go to manufacturing and … everybody just hopes they’re manufactured correctly. If they perform badly, they hope you won’t notice.
In order to test an antenna’s performance, you need a tool like the N1201SA SWR meter. The asking price of almost $200 is much less than the thousands of dollars these devices usually cost. So what’s the catch? One limitation of the N1201SA is that it only measures up to 2.7 GHz. So it’ll be great for testing 2.4 GHz receiver antennas, 900 MHz Crossfire or R9 antennas, or anything of lower frequencies. The one place it won’t work is with 5.8 GHz FPV antennas–unfortunately, where it might be the most useful.
If you’ve ever heard stories about FrSky receiver antennas being the wrong length, resulting in reduced range and failsafes, this is the tool you’d use to detect and fix that problem.